Composition for acetylene production and method for treating lime slurry by-product from acetylene production

ABSTRACT

The use of a settling aid in the reactor during acetylene production results in the by-product lime slurry being easier to handle and allows the acetylene producers to use different sources of calcium carbide as well as the calcium carbide manufacturers to use different sources of raw materials to make calcium carbide.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a composition for use in the productionof acetylene gas and a method for treating the lime slurry by-productfrom acetylene gas production to make the slurry easier to handle andavoid the need for special handling equipment for the sediment. Thepresent invention allows an acetylene producer to use calcium carbidefrom a variety of sources and allows the calcium carbide producer moreflexibility in sourcing raw materials.

[0003] 2. Art Related to the Invention

[0004] Calcium carbide (CaC₂) is produced in an electric furnace byheating a mixture of lime and carbonaceous materials such as coke, coal,or charcoal. The heat of the furnace converts the mixture to calciumcarbide and carbon monoxide. Both the source of lime and the source ofcarbonaceous material have different impurities which are carriedthrough to the calcium carbide. Typically, industrial grade calciumcarbide, sold for the generation of acetylene gas, contains about 2% toabout 5% by weight impurities. The primary impurities are metals andmetal alloys such as silicon, iron, aluminum and magnesium.

[0005] One of the conventional methods for producing acetylene (CH≡CH)is the action of water on calcium carbide. One of the by-products fromsuch production is a lime slurry. This lime slurry essentially comprisescalcium hydroxide, water, and whatever impurities were present in thecalcium carbide.

[0006] The lime slurry is pumped from the reactor to settling tankswhere water is removed for recycling and sediment forms. Water from theslurry is saturated with acetylene and is therefore preferred as asource of water in the reactor. By using recycled water, the overallefficiency of the reaction is increased. Thus, it is important that theslurry settle rapidly and form the sediment.

[0007] Once water has been removed from the slurry for recycling and thesediment formed in the holding tanks, water is added to the sediment toreslurry the sediment and make the sediment easier to pump.

[0008] It has been found that the lime slurry and the resulting sedimenthave different physical characteristics, especially settlingcharacteristics and reslurrying characteristics, depending on the sourceof calcium carbide. These different characteristics have been attributedto the impurities which are present in the calcium carbide. For example,when the calcium carbide is produced from petroleum coke, the limeslurry settles slowly, the sediment is diffuse and readily reslurries.On the other hand, when metallurgical coke is used to make the calciumcarbide, the lime slurry settles quickly, the sediment is dense and isdifficult to reslurry.

[0009] Because of the differences in t-he settling properties of thelime slurry and the reslurrying characteristics of the sediment,different mechanical equipment is employed to handle the sediment. Thus,acetylene producers generally do not switch calcium carbide sources.Furthermore, calcium carbide producers are forced to standardize theirsources of raw materials so as to maintain the same type of impuritiesin their calcium carbide. Needless to say, this means that the calciumcarbide manufacturers are unable to switch their sources of rawmaterial, thereby increasing the overall cost for production of calciumcarbide which, in turn, increases the overall cost for production ofacetylene.

[0010] There is a need for a simple and inexpensive way to treat thelime slurry by-product from the acetylene manufacturing process so as toincrease the settling rate while improving the handling properties ofthe sediment which results from the lime slurry so as to reslurryreadily and to be easy to handle, even after sitting a number of days inthe holding tanks.

SUMMARY OF THE INVENTION

[0011] It has now been discovered that a settling aid, present in thereactor during production of acetylene, can effect the settling propertyof the by-product lime slurry and can effect the handling properties ofthe sediment. The use of the settling aid of the present invention hasbeen found to increase in the rate of settling of the lime slurry, thusincreasing the rate of recycling of water from the slurry. It has alsobeen found to improve the reslurrying properties of the sediment therebyassisting in removal and handling of the sediment.

[0012] Specifically, it has been found that by employing the presentinvention, no special equipment is necessary for handling-the limeslurry or the sediment that results from the lime slurry. Furthermore,it has been found that the acetylene manufacturer may vary the sourcesof calcium carbide without having to modify or change the lime slurryand sediment handling equipment. The present invention also allows thecalcium carbide manufacturer to vary the sources of raw material. Bothof these allow for lower production costs of calcium carbide andacetylene.

[0013] Furthermore, it has been found that by employing the presentinvention there is no detrimental effect to the reactor or the reactionthat occurs in the acetylene reactor. The settling aid, although presentin the reactor, does not affect the rate of reaction and has been foundto carry through the reactor and into the lime slurry.

[0014] Furthermore, it has been found that the settling aid settles withthe sediment and is not carried through into the recycled water. Allthis allows the acetylene manufacturer to continue his operations asnormal with the improved benefit of allowing him to change the sourcesof calcium carbide.

[0015] Additionally, it is important that the sediment can be reslurriedafter a period of time. It has been found that the sediment of thepresent invention can sit for a number of days and still be reslurriedand effectively pumped.

[0016] The settling aid of the present invention can be added directlyto the acetylene reactor by the acetylene manufacturer or it can beadded to either or both of the reactants, calcium carbide and water,prior to introduction into the acetylene reactor.

[0017] The settling aid may also be added directly to the lime slurry asit leaves the reactor, however, it is preferred that the settling aid bepresent in the reactor during the formation of the lime slurry.

[0018] It has also been discovered that the settling aid can be added tothe top of the sediment in the holding tank prior to reslurrying thesediment and that such top treatment will beneficially effect thereslurrying properties of the sediment. Since such a treatment onlyeffects the handling properties of the sediment and not the initialsettling properties of the lime slurry and recycling of water to thereactor, it is not a preferred embodiment of the present invention.

[0019] The calcium carbide manufacturer can form a mixture of thecalcium carbide and the settling aid and sell the mixture to theacetylene manufacturer. This allows the calcium carbide manufacturer tovary the source of raw material used to make calcium carbide withouttroubling the acetylene manufacturer.

[0020] Suitable settling aids for use in the present invention comprisephosphates, chelating agents, alkali metal chlorides, carbonates,carboxylic acids, sulfur compounds, clays, sugars, silica fume, andlignin.

[0021] Broadly, the present invention is a method for treating a limeslurry by-product from acetylene production to make the lime slurry andits resulting sediment easier to handle, said method comprising:

[0022] reacting water with calcium carbide in a reactor to formacetylene and a lime slurry by-product in the presence of a settlingaid; and

[0023] recovering said lime slurry by-product with said settling aidpresent therein.

[0024] The method of the present invention can also be broadly definedas an improvement in the method for making acetylene gas from calciumcarbide and water where a lime slurry is a by-product, the improvementcomprising:

[0025] reacting said water and said calcium carbide in a reactor in thepresence of a settling aid to form acetylene gas and a lime slurryby-product; and

[0026] recovering said lime slurry by-product with said settling aidpresent therein.

[0027] The method of the present invention can also be characterized astreating a lime slurry by-product from an acetylene manufacturingprocess or a sediment from the lime slurry by-product from the acetylenemanufacturing process with a settling aid to improve the settlingproperties of the lime slurry and the handling properties of thesediment.

[0028] Thus, the present invention can be characterized as a new use ofa settling aid where that new use is as an additive to an acetylenereaction and/or the by-product lime slurry and sediment.

[0029] The present invention has also led to discovery of a newcomposition for use in the production of acetylene, that compositionbeing broadly defined as comprising a homogeneous mixture of calciumcarbide and a settling aid.

[0030] As brought out above, it has been found that the settling aidwhich is present in the reactor ends up in the lime slurry, is carriedinto the settling tanks and ultimately stays with the sediment in thesettling tanks. Thus, it is not carried away with the recycling water.Furthermore, it has been found that a number of the settling aids areenvironmentally friendly and, thus, the sediment with the settling aidtherein is readily disposable without the need for further handling ortreatment of the sediment.

[0031] Furthermore, it has been found that the present invention has nodetrimental effect on the recycle water and, in fact, has the beneficialeffect of increasing the rate of settling thereby increasing the rate ofavailability of the recycle water.

[0032] These and other aspects of the present invention may be morefully understood by reference to the following drawings and detaileddescription of the invention that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 illustrates the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0034]FIG. 1 illustrates the method of the present invention whereinacetylene reactor 10 receives reactants, calcium carbide 12 and water 14to produce acetylene 16 and by-product lime slurry 18. By-product limeslurry 18 can have a settling aid present therein. Lime slurry 18 isnormally pumped from acetylene reactor 10 to settling tanks. From thesettling tanks, recycled water 20 is removed and recycled back to theoriginal water 14. Sediment 22 forms in the settling tanks and isremoved from the settling tanks, usually by reslurrying and pumping thereslurried sediment out of the tanks, and into a land fill.

[0035]FIG. 1 illustrates the use of the settling aid in accordance withthe present invention. The points of addition of the settling aid areshown by employing dotted lines in FIG. 1.

[0036] Specifically, settling aid 30 can be added directly to acetylenereactor 10 along with the other reactants of calcium carbide 12 andwater 14. The addition of settling aid 30 to reactor 10 is done in aconventional manner using conventional equipment, such as a sprayslurry.

[0037] Alternatively, settling aid 32 is added to water 14 which isthen, in turn, added to reactor 10 as a reactant. The water and settlingaid are mixed in a conventional manner using conventional equipmentprior to its addition to reactor 10.

[0038] As yet another alternative to the present invention, settling aid34 is added by the acetylene manufacturer to the calcium carbide 12. Thecalcium carbide and settling aid are mixed in a conventional mannerusing conventional equipment. The mixture of calcium carbide andsettling aid is then added to reactor 10 as a reactant.

[0039] A still further alternative to the present invention is for theacetylene manufacturer to employ composition 36 which comprises calciumcarbide and a settling aid. Composition 36 is added to reactor 10 in aconventional manner using conventional equipment. Composition 36 isprovided to the acetylene producer by the calcium carbide manufacturer.In this way, the acetylene manufacturers need not concern themselveswith how much of the settling aid to add to reactor 10 directly or toreactants, calcium carbide 12 and water 14.

[0040] Alternatively, a combination of two or more of 30, 32, 34 and 36can be employed. For example, the calcium carbide manufacturer couldemploy a portion of composition 36 in conjunction with calcium carbide12. In this way, the acetylene manufacturer would be employing twodifferent sources of calcium carbide, one without the settling aid andone with the settling aid. This combination of calcium carbide sourceswould allow the acetylene manufacturer to practice the present inventionby having the settling aid present in the reactor during the reactionwhile allowing the acetylene manufacturer flexibility of obtainingcalcium carbide from different sources.

[0041] Finally, as another alternative, the settling aid can be added tothe by-product lime slurry or sediment. Settling aid 38 can be added tolime slurry 18 as it is pumped from the reactor 10 or when it is in thesettling tanks. Adding settling aid 38 to the out flow of reactor 10 orto the settling tanks is not preferred since the lime slurry is formedin the reactor and may start to exhibit handling problems in reactor 10.This addition is done in a conventional manner using conventionalequipment to insure that the settling aid is homogeneously mixed intothe lime slurry.

[0042] Settling aid 40 can be added to sediment 22 as it sits in thesettling tanks. Adding settling aid 40 to sediment 22 is not preferredbecause the increased settling rate is not obtained, even thoughimproved sediment handling characteristics are obtained. Such anaddition is done in a conventional manner using conventional equipment.

[0043] Thus, it is preferred in accordance with the present invention,that the settling aid be present in the reactor during the reaction. Themixing of the settling aid with the other reactants is done in aconventional manner using conventional equipment. The addition of thesettling aid to either the reactants or the reactor is done in aconventional manner using conventional equipment. The addition of thecomposition of calcium carbide and settling aid to the reactor is alsodone in a conventional manner using conventional equipment. Finally, theaddition of the settling aid to the lime slurry or the sediment is donein a conventional manner using conventional equipment.

[0044] The formulation of the composition of calcium carbide andsettling aid by calcium carbide manufacturers is done in a conventionalmanner using conventional equipment so as to form a homogeneous mixtureof the two. The two components, calcium carbide and the settling aid,are added in the appropriate amounts and mixed so as to form ahomogeneous mixture. This mixture is formed after the calcium carbidehas been made and crushed to an appropriate size for use in acetylenemanufacture.

[0045] The amount of settling aid used in the present invention issuitably an effective amount, effective to improve the settlingproperties and/or handling properties of the by-product lime slurry andsediment. Preferably, the settling aid is present in an amount of lessthan or equal to about 25% by weight calcium carbide in the reactor.More preferably, the settling aid is present in an amount of about 0.01%to about 25% by weight based on the calcium carbide used in the reactor.More preferably, the amount of settling aid used in the presentinvention is less than or equal to about 1% by weight of the calciumcarbide that is used in the reaction. Good results have been obtainedwhen employing the settling aid in an amount of about 0.1% to about 1.0%by weight calcium carbide in the reactor.

[0046] Suitably, the composition of the present invention is ahomogeneous mixture comprising a settling aid in an amount of less thanor equal to about 20% by weight mixture and calcium carbide in an amountof greater than or equal to about 80% by weight mixture. Preferably, thecomposition comprises about 0.01% to about 20% by weight settling aidand about 99.99% to about 80% by weight calcium carbide. Morepreferably, the composition of the present invention is a mixture thatcomprises a settling aid in an amount of less than or equal to about 1%by weight mixture and calcium carbide in an amount of greater than orequal to about 99% by weight mixture. Good results have been obtainedwith the present invention with a composition comprising a mixture ofabout 0.1% to about 1.0% by weight settling aid and about 99.9% to about99% by weight calcium carbide.

[0047] Phosphates which are suitable as settling aids in accordance withthe present invention include phosphate salts and molecular dehydratedphosphates. Suitable phosphate salts include sodium, potassium andammonium salts of phosphate. Specifically, suitable phosphate saltsinclude:

[0048] monobasic sodium phosphate (NaH₂PO₄),

[0049] dibasic sodium phosphate (Na₂HPO₄)

[0050] tribasic sodium phosphate (Na₃PO₄),

[0051] monobasic ammonium phosphate (NH₄H₂PO₄),

[0052] dibasic ammonium phosphate (NH₄)₂HPO₄),

[0053] monobasic potassium phosphate (KH₂PO₄),

[0054] dibasic potassium phosphate (K₂HPO₄), and

[0055] tribasic potassium phosphate (K₃PO₄)

[0056] Monobasic sodium phosphate is preferred.

[0057] Suitable molecular dehydrated phosphates include:

[0058] sodium tripolyphosphate (Na₅P₃O₁₀),

[0059] hexametaphosphate (((CH₃)₂N)₃PO), and

[0060] tetrapotassiumphosphate (K₄P₂O₇).

[0061] Suitable chelating agents which can be employed as a settling aidin accordance with the present invention includeethylenediaminetetraacetic acid ((HOOCCH₂)₂NCH₂CH₂N (CH₂COOH)₂) (EDTA)and salts of EDTA. Other suitable chelating agents include salts ofnitrolotriacetic acid (N(CH₂COOH)₃) and sodium citrate (C₆H₅O₇Na₃).

[0062] Suitable alkali metal chlorides which can be used as settlingaids in accordance with the present invention include lithium chloride(LiCl), sodium chloride (NaCl), potassium chloride (KCl). Sodiumchloride is preferred because of expense.

[0063] Suitable carbonates which can be used as settling aids inaccordance with the present invention include sodium carbonate (Na₂CO₃),calcium carbonate (CaCO₃) and potassium carbonate (K₂CO₃).

[0064] Suitable carboxylic acids which can be used in accordance withthe present invention include citric acid (C₆H₈O₇), tartaric acid(C₃H₄O₅) and acetic acid (C₂H₄O₂).

[0065] Suitable sulfur compounds which can be used in accordance withthe present invention include sodium bisulfite (NaHSO₃), sodium sulfite(NA₂SO₃) and sodium sulfate (Na₂SO₄). Sodium bisulfite is preferred.

[0066] Suitable clay and clay minerals which can be used in accordancewith the present invention include kaolinite, montmorillonite,attapulgite, illite, bentonite, and halloysite. Bentonite is preferred.

[0067] Suitable sugars which can be used in accordance with the presentinvention include glucose, sucrose, and fructose.

[0068] Silica fumes can also be employed as a settling agent inaccordance with the present invention. Silica fume is conventionallyavailable as a by-product from manufacturers of ferrosilicon and siliconmetal. Silica fume is also referred to as microsilica.

[0069] More specifically, silica fume is produced by capturing thefinely divided particles from stack gases of electric arc furnaces.Silica fume is a pozzolan, i.e., it combines with lime and moisture atordinary temperature to form compounds having cementitious properties.The main constituent is silicon dioxide (SiO₂) and it is usually presentin an amount of at least about 80%.

[0070] An amorphous silica fume that is eminently suitable for use inthe present invention is obtained as a by-product in the production ofsilicon metal or ferrosilicon in electric reduction furnaces. In theseprocesses, fairly large quantities of silica are formed as dust which isrecovered in filters or other collection apparatus. Such silica fume canbe obtained from Elkem Metals Company, Pittsburgh, Pa., US.

[0071] The amorphous silica used in the present invention is composedsubstantially of sub-micron, spherical particles. The spherical shapetogether with its fineness pozolanic activity makes it surprisinglyuseful in accordance with the present invention.

[0072] For example, the amorphous silica fume particles may consist ofat least 60 to 90% by weight of SiO², will have a real density of2.20-2.25 g/cm³ and will have a specific surface area of 18-22 m²/g, theparticles being substantially spherical, and wherein at least 90% byweight of the primary particles have a particle size of less than 1micron. Of course, variation of these values is readily possible. Forexample, the silica fume may have a lower SiO₂ content.

[0073] Lignin is a major non-carbonate constituent of wood and often aby-product from paper processing. Lignin sulfonate can also be used inthe present invention.

[0074] One or more settling aids can be used in the present invention.When more than one settling aid is used, the amount of combined settlingaids must be within the parameters of the present invention, e.g. withinabout 0.01% to about 25% by weight calcium carbide.

[0075] It is important for slurry to settle quickly but not become toodense to prevent reslurrying. A balance must be struck between the rateof settling and the ability for the sediment to be reslurried andsubsequently pumped. Thus, the optimal amount of settling aid may varyfrom settling aid to settling aid within the parameters set forth inthis application. The optimum amount of settling aid can be readilydetermined.

[0076] Conventionally, the slurry has a solids content of about 30% toabout 40% by weight, the sediment has a solids content of about 70% toabout 80% by weight, and the reslurried sediment has a solids content ofabout 30% to about 40% by weight.

[0077] These and other aspects of the present invention may be morefully understood by reference to one or more of the following examples.

EXAMPLE 1

[0078] This example illustrates the use of various settling aids inaccordance with the present invention.

[0079] Into a 500 ml cylinder, 400 ml of water, 60 grams of calciumcarbide and a certain amount of a settling aid were added. Acetylene gaswas produced and, after production of the gas, a lime slurry with thesettling aid remained in the cylinder.

[0080] The Table below lists the settle aids tested, the amount ofsettle aid employed based on the weight of calcium carbide, whether thesettling aid was mixed into calcium carbide and the mixture of calciumcarbide and settling aid (S) added to the cylinder or whether thesettling aid was added to the water and the mixture of water andsettling aid (W) added to the cylinder.

[0081] Also listed in the Table below is the rate of settling (ml/hour)and the density of the sediment over a period of days.

[0082] In order to determine settling rate and density of the sediment,a portion of the lime slurry was poured into a graduated cylinder.

[0083] Settling was determined immediately by measuring the speed atwhich the sediment dropped in the cyclinder over time. The rate wasmeasured in milliliters per hour, the milliliters corresponding to theincrements on the graduated cylinder. Thus, the settling rate is that ofthe lime slurry in the first hour after completion of the reactionbetween the water and the calcium carbide.

[0084] The density of the sediment was determined by thrusting a glassrod into the sediment and characterizing the pressure that was necessaryto thrust the rod into the sediment. These densities were graded on ascale of 1 to 5 with 5 being the less dense, no resistance, and 1 beingthe most dense. These densities were measured over a six day period.LIME SLURRY SETTLING TESTS St Settling Aid & Amount* rate Day 1 Day 2Day 3 Day 4 Day 5 Day 6 1 3.33% Sod.P (W) 1.67 5 5 5 5 5 5 2 1% salt (S)1.95 n/a n/a 5 5 5 5 3 .5% salt (S) 2.14 n/a n/a 5 5 5 5 4 1% Sod.P (S)2.33 n/a 5 5 5 5 5 5 .75% salt.25% clay(s) 2.43 n/a n/a n/a 5 5 5 6 .5%Sod P (S) 2.62 n/a 5 5 5 5 5 7 3.333% salt (W) 2.81 5 5 5 5 5 5 8 2%Clay (S) 2.81 n/a 5 5 5 5 5 9 1.67% salt (s) 2.81 n/a n/a 5 5 5 5 10 4%Clay (S) 3.19 4 4 3 3 2 2 11 carbide 3.29 4 4 3 2 2 2 12 .75% Sod.P 25%clay (S) 3.36 n/a n/a n/a 5 5 5 13 1% Clay (S) 3.48 n/a 5 5 5 5 5 14 8%Clay (S) 4.00 5 4 4 3 3 3

[0085] The amount of settling aid added is given as a percent of calciumcarbide. Thus, in Test 1, 3.33% Sod. P (W) means that 2 grams of sodiummonobasic phosphate was added and mixed into the water before combiningthe water with the calcium carbide. In Test 2, 1% salt (S) means that0.6 gram of sodium chloride was added to the calcium carbide and thenthe mixture of salt and calcium carbide combined with water to makeacetyline gas.

[0086] It will be noted that Test 11 had no settling aid present. Tests5 and 12 employed two settling aids together.

[0087] It should also be noted that, even though the sediment in thetests above had sat for six days, it was still fluid enough to bereadily movable.

EXAMPLE 2

[0088] This example illustrates field tests which were performed oncommercial scale acetylene reactors.

[0089] Monobasic sodium phosphate in an amount of 0-2% by weight calciumcarbide was added to 600 pounds (270 kg) of calcium carbide and used ina reactor to form acetylene.

[0090] The resulting sediment was found to readily reslurry and to bepumpable.

EXAMPLE 3

[0091] This example illustrates that a top treatment of the sedimentusing the settling aid of the present invention also works.

[0092] An untreated lime slurry was allowed to settle in two separatebeakers so as to form a sediment in both beakers. After settling,monobasic sodium phosphate was added to the top of the sediment in onebeaker as a settling aid. The other beaker was not treated. Water isthen added to both sediments to reslurry the sediments.

[0093] The sediment in the treated beaker is readily reslurried andpumpable. The untreated slurry is not readily reslurried and is moredifficult to move than the top treated sediment.

EXAMPLE 4

[0094] This example illustrates the present invention with differentcalcium carbides.

[0095] Two calcium carbides are employed, one made with petroleum cokeand another made with metallurgical coke. Into two different beakerseach of the calcium carbides and water are added along with 1% by weightof monobasic sodium phosphate. Each beaker is placed under a hood toallow for generation of acetylene gas. After production of acetylenegas, the sediment with the settling aid is allowed to settle. The twosediments are found to have the same characteristics.

[0096] It will be understood that the claims are intended to cover allchanges and modifications of the preferred embodiments of the inventionherein chosen for the purpose of illustration which do not constitute adeparture from the spirit and scope of the invention.

What is claimed is:
 1. A method for treating a lime slurry by-productfrom acetylene production to make the lime slurry easier to handlecomprising: reacting water with calcium carbide in a reactor to formacetylene and a by-product lime slurry in the presence of a settlingaid; and recovering said lime slurry with said settling aid presenttherein.
 2. The method of claim 1 wherein the settling aid is present inan amount of less than or equal to about 25% by weight calcium carbide.3. The method of claim 1 wherein said settling aid is selected from thegroup consisting of phosphates, chelating agents, alkali metalchlorides, carbonates, carboxylic acids, sulfur compounds, clays,sugars, silica fume, and lignin.
 4. The method of claim 1 furthercomprising the step of adding said settling aid to said reactorindependent of said water and said calcium carbide.
 5. The method ofclaim 1 further comprising the step of adding said settling aid to saidwater before adding said water to said reactor.
 6. The method of claim 1further comprising the step of adding said settling aid to said calciumcarbide before adding said calcium carbide to said reactor.
 7. In amethod for making acetylene from calcium carbide and water where aby-product of lime slurry is formed and water is recycled from said limeslurry resulting in a sediment, the improvement comprising treating saidsediment with a settling aid; and reslurrying said sediment with saidsettling aid present therein.
 8. In a process for making acetylene fromcalcium carbide and water wherein a by-product is a lime slurry, theimprovement comprising adding a settling aid to the by-product limeslurry as it exits the reactor such that said settling aid is present insaid lime slurry in settling tanks.
 9. A composition for use in theproduction of acetylene, said composition comprising a mixture ofcalcium carbide and settling aid.
 10. The composition of claim 9 whereinthe settling aid is present in an amount of less than or equal to about20% by weight calcium carbide.
 11. The composition of claim 9 whereinsaid settling aid is present in an amount of about 0.01% to about 20% byweight composition and said calcium carbide is present in an amount ofabout 99.99% to about 80% by weight composition.
 12. In a method formaking acetylene from calcium carbide and water in a reactor to formacetylene and a by-product of lime slurry, the improvement comprisingadding a settling aid to the reactor such that said settling aid ispresent in the reactor during production of acetylene and combines withthe lime slurry by-product.
 13. The method of claim 12 wherein saidsettling aid is added to said calcium carbide prior to addition of thecalcium carbide to the reactor.
 14. The method of claim 13 wherein saidsettling aid is added to the water prior to addition to the reactor. 15.The method of claim 13 wherein said settling aid is added to saidreactor independent of the addition of said calcium carbide and saidwater.